Ecosystems

Question 1

6 levels of ecological organisation?

Answer 1

species
population
community
ecosystem
biome
biosphere

Question 2

Define ecology

Answer 2

Study of the relationship between organisms and their environment.

Question 3

Define species

Answer 3

Organisms with similar characteristics that produce fertile offspring when bred together.

Question 4

Define population

Answer 4

A group of individuals of the same species that occupy the same habitat at the same time.

Question 5

Define community

Answer 5

A group of populations of different species occupying the same place at the same time and interacting.

Question 6

Define ecostytem

Answer 6

Includes all biotic and abiotic factors in an area that function as a unit.

Question 7

Examples of abiotic factors

Answer 7

• weather (sun/cloud/rain etc)
• climate (temperature/humidity etc)
• air composition (N2, O2, CO2 etc)
• edaphic factors (pH/nitrates/nitrite etc)
• water salinity

Question 8

Define biome

Answer 8

Large scale ecosystems defined by abiotic factors such as climate, relief, geology, soils, vegetation.

Question 9

Define biosphere

Answer 9

The area of the planet where organisms live, including the ground, water, atmosphere and underground. e.g. desert, scrub, tundra etc

Question 10

Define niche

Answer 10

The role of an organism in its ecosystem e.g. where it lives (structural niche), what it feeds on (feeding niche), when it breeds

Question 11

`Habitat

Answer 11

The area where an organism/community lives.

Question 12

How is biomass measured?

Answer 12

mean biomass in each organism X total no. of organisms in trophic level

Question 13

What are the limitations of biomass?

Answer 13

They only take into account the biomass at a particular time, excluding seasonal changes.
Small samples may not be representative but large samples are not ethical.

Question 14

What is and isn’t included in biomass?

Answer 14

Water is not counted (organisms are dried) so that only organic/carbon/energy-containing compounds are counted.

Question 15

Biomass units

Answer 15

Land - gm^(-2)
Water - gm^(-3)

Question 16

Define biomass

Answer 16

The mass of living material in a particular place of particular organisms.

Question 17

Define ecological efficiency

Answer 17

The efficiency of energy transfer through food chains (usually around 10%).

Question 18

Reasons for energy loss in plants (5)

Answer 18

• Reflection
• Transmission (misses chloroplasts)
• Other limiting factors
• Wrong wavelength
• Energy loss in reactions (respiration etc)

Question 19

Gross primary production (GPP)

Answer 19

Total energy stored by producers

Question 20

Net primary productivity (NPP)

Answer 20

Energy left after respiration in plants (some energy converted to ATP and some lost as heat energy)

Question 21

Productivity equation

Answer 21

NPP = GPP - energy used in respiration

Question 22

Reasons for low ecological efficiency between consumers (4)

Answer 22

• not all of the biomass is consumed (roots/bones etc)
• energy dissipated as heat
• not all of the organism is digestible (egested as faeces)
• energy lost in excrement (faeces/urine)

Question 23

Ecological efficiency equation

Answer 23

(biomass after transfer / biomass before transfer) X 100

Question 24

Intensive farming techniques (8)

Answer 24

• selective breeding –> fast growth rates
• high digestibility diets –> remove fibres/cellulose to increase ecological efficiency
• restricted movement –> minimise energy loss
• ventilation systems –> minimise energy loss via thermoregulation
• exclusion of predators –> no biomass eaten by predators other than humans
• slaughtered young –> make space for new animals to grow and put on biomass
• growth hormones
• antibiotics

Question 25

Define decomposers

Answer 25

Saprophytic organisms that carry out extracellular digestion by secreting digestive enzymes to breakdown and absorb organic matter. e.g. fungi and bacteria

Question 26

Define detritivores

Answer 26

Small animals that feed on detritus (fragments of decomposing material) and speed up the decomposition process by increasing surface area for the decomposers. e.g. worms, ants, woodlice

Question 27

What are the five main forms of nitrogen?

Answer 27

- N2(g) - NH3 and NH4+ (ammonia dissolves in water to form ions) - NO2- and NO3- - proteins (amino acids) - DNA and RNA (nitrogenous bases)

Question 28

What forms of nitrogen can and can't be used by plants?

Answer 28

Plants can only directly use nitrates. (cannot use nitrites, ammonia or ammonium ions)

Question 29

What are stages of succession called?

Answer 29

seres

Question 30

Primary vs secondary succession

Answer 30

Primary - land is newly formed and contains no soil or organic matter Secondary - soil is present but there is an absence of plants and animals

Question 31

Succession stage 1

Answer 31

- Pioneer species colonise the land (algae, lichen etc) - Highly adapted to survive in extreme conditions (phototrophs, produce lots of spores/seeds, nitrogen fixing abilities)

Question 32

Succession stage 2

Answer 32

- Rock weathers and plants die forming soil particles - Decomposed plants provide humus (organic matter) - New plant species are able to grow (secondary colonisers such as mosses)

Question 33

Succession stage 3

Answer 33

- Conditions improve and new plant species arrive (tertiary colonisers) - Minimal amount of soil, low water absorption - Plants adapted to survive with low water availability (xerophytes)

Question 34

Succession stage 4

Answer 34

- Rocks continually weathered and plants decompose increasing amount of soil and humus - More soil, higher water absorption, improved abiotic conditions - Small flowering bushes, shrubs and trees grow

Question 35

Succession stage 5

Answer 35

- Climax community forms - Usually one or two dominant species - Mid biodiversity due to high competition

Question 36

Define succession

Answer 36

The progressive replacement of one dominant type of species or community by another in an ecosystem until a stable climax community has been established.

Question 37

Define deflected succession

Answer 37

Human influences that prevent a climax community from being established. This creates an artificial climax called a plagioclimax.

Question 38

What is an artificial climax called?

Answer 38

plagioclimax

Question 39

Causes of deflected succession (3)

Answer 39

- Grazing and trampling of vegetation - Removing existing vegetation to grow crops - Burning forests to provide ash for nutrient rich soil to increase biodiversity